Electrical system



Sept 14 l954 w. E. BRADLEY ELECTRICAL SYSTEM Filed Jan. 26, 1951 MEQ/MNNQ SMQ IIEI Q Cmmdhy Sms @n .S

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Patented Sept. 14, 1954 12,689,269 .ELECTRICAL SYSTEM 'l/'VilliamBradley, New Hope, rPa., 'assigner Sto Philco Corporation, Philadelphia,iPa., a'corporation of Pennsylvania nppiieaaonianuary26,1951,-seriaiNo-sio6t 13 Claims. i

The present 'invention relates to electrical systems and moreparticularly to cathode-raytube systems in which the position off thebelectron beam relative to a `beam Yintercepting member ci the tube iscontrolled by Aan indexing member so arranged in cooperativerelationship with the beam intercepting member to produce a lsignalWhose time of occurrenceis indicative of `thetirne at which thecathode-raybeamattains a predetermined position.

The invention is particularly adapted 'for and will be describedinconnection Witha-color television image presentation system utilizingu'a single cathode-ray tube having a "beam intercepting, imageformingscreen member comprising vertical stripes of luminescent\materials. These `strips are ypreferably arranged inlaterally-displaced color triplets, each triplet 'comprising threevertical phosphor stripes Whichrespo'n'd to electron impingement toproduce :light of the n diierent primary colors. The order iofarrangement or the stripes may be such that the normalhorizontally-scanning -cathode-'ray beam "produces red, green and bluelight successively. From a color television receiver there 'arethensupplied three separate video signals, each indicative oi a dierentprimary colorcomp'onent oi a televised scene, which signals Yare sampledsequentially and utilized to 'contrdl'the intensity of the cathode-raybeam. Forjproper color rendition, it is then required that, as thephosphor stripes producing each of the 'primary colors of light areimpinged by the cathode-'ray beam, the intensity of the beam besimultaneously ccntrolled in response to the 'contemporaneous value ofthe video signal representing the corresponding color component of `thetelevised image. However, since the rate at Which the beam scans acrossthe phosphor stripes of the screen 'may be variable, due, for example,to non-linearity of the beam deilecting signal, the times .at which thesamples of the several video color signals should be taken willgenerally not occur 'exactly periodically. To obtain proper timing 'of'the sampling operations, it is 'therefore desirable to derive signalsindicative of the instantaneous position of the cathode-ray beam uponthe imageforming screen, and to `utilizethese indexing signals tocontrol the times at which samplings of the several color signals areeffected. 'The said index-:ing signals maybe derived from a plurality ofstripe members arranged on the 'beainin'tercepting screen structure eachadjacent a 'triplet so that, when the beam scans "the screen, theindexing stripes are excited in `spaced time se- 2 quence to thescanning fof the color triplets and aiseriesof pulse'sis generated in asuitable output electrode system of 'thecathcde-ray tube.

The indexing stripes'may comprise a 4material havingsecondaryeemissiveproperties which diferfrom the secondary-emissive properties of theremaining portions of the beam intercepting structure. Foriexalmple, theindexing stripes may consist of a high 'atomic number material such asgold, platinum or tungsten or may consist of certain 'mixtures includingcesiurn or cesium oxidaandthe remainder of the beaminterceptingstructur'e maybeprovided with a coating of a material-having a fdetachably different `secondary-emissive ratio such as acoating of aluminimi, 'which coating also serves as a light relectingymirror `for 'the phosphor stripes in accordance vwith well knownpractice. With such an arrangementthe indexing signals may bederived-from -a collector electrode arranged in the vicinity of thesCreenStruCture. Alternately, the indexing stripes vmay consist of afluorescent material `such as zinc oxide having a spectral output in thenon-visible light 'region and the indexing signals-may be derived from asuitable photoelectric cell arranged, forexample, in a side wall portionof the cathode-ray `tube out of the path of the cathode-ray vbeam andfacing the beam intercepting surface of the screen structure.

Lln practice there exists the danger that the normally detectablevoltage indicating the impingement `of the beam onto 'the indexingstripes may Abe masked or at least contaminated by spurious voltages.More particularly, it is found that, at the `high accelerating voltagesof the order of l0 to r20 kilovolts used in the cathode-ray tubes foi'the 'systems under consideration, only a relatively small difference vinthe secondaryemis'sive ratio 'of the materials of the indexing stripesand 'of the remainder of the screen structure can be realized and thatin the heretofore proposed systems the presence oi video signals andnoise voltages in the collector 'electrode system may'signii'lcantlydiminish the effective value of the indexing signal. Similarly, in thoseinstanc'es in which the indexing signal is produced by means of aphoto-electric detector and an indexing stripe 'comprising a fluorescentmaterial which produces light in the non-visible region of the spectrum,'the detector may be also actuated by soft Xerays which are produced bythe high voltage beam or by extraneous light 'from sources external to'the cathode-ray tube or from the phosphor stripes "of the lcolortriplets, the latter light in some instances penetrating the aluminummirror coating superimposed on the color stripes.

It is an object of the invention to provide an improved cathode-ray tubesystem of the type in which the position of the electron beam relativeto a beam intercepting member is controlled by an indexing member.

Another object of the invention is to provide a cathode-ray tube systemof the type in which the position of the electron beam is controlled byan indexing member and in which a clearly dened indexing signal voltageis generated.

A further object of the invention is to provide a cathode-ray tubesystem in which the intensity of the indexing signal voltage is madesubstantially independent of the video information applied to thesystem.

A specic object of the invention is to provide a cathode-ray tube systemin which normally contaminating influences have substantially nosignicant effect on the indexing signal produced by the cathode-raytube.

These and further objects of the invention will appear as thespecication progresses.

In accordance with the invention, the foregoing objects are achieved byemploying a cathode-ray tube having disposed therein a beam interceptingstructure comprising beam position indicating elements arranged inpredetermined geometric relationship to other portions of the beamintercepting structure. These beam position indicating elements, asabove pointed out, may be characterized by values of secondary-emissiveratio or by spectral emission characteristics which differ from thosecharacterizing other regions of the beam interceptive structure whenelectrons of the cathode-ray beam impinge thereon. In order to produce aclearly dened indexing signal readily distinguishable from contaminatinginuences, there is provided, as an integral part of the cathode-ray tubesystem, means whereby the intensity of the electron beam is momentarilyand automatically increased to a given predetermined value during theintervals when the beam impinges on the indexing stripes. Preferably,the intensity of the beam is momentarily increased to a value greaterthan the maximum beam intensity produced by the video signals applied tothe cathode-ray tube. In the case of cathode-ray tube systems in whichthe magnitude of the indexing signal is determined by the secondaryemission ratio of the material of the indexing stripe, it has been foundthat, by so modifying the beam intensity at the instant the beamimpinges on the indexing stripes, the intensity of the indexing signalmarkedly differs from the intensity of spurious voltages generated bythe portions of the beam interceptive member when the beam impinges atits normal intensity on such other portions. Similarly, in the case ofcathode-ray tube systems in which the indexing voltage is derived fromthe non-visible light generated when the beam impinges on a iiuorescentindexing stripe, the output signal produced is greater, by orders ofmagnitude, than any spurious voltage produced by contaminatinginfluences internal or external to the cathode-ray tube.

The invention will be described in greater detail with reference to theappended drawings forming part of the specification and in which:

Figure l is a diagram partly schematic showing a cathode-ray tube systemin accordance with the invention and embodying certain modications laterto be described in detail,

Figure 2 is an enlarged plan view partly cut away of a portion of abeam-intercepting indexing screen member which may be used in thecathode-ray tube of the system shown in Figure 1 and,

Figure 3 is a graph showing the relative size and phases of certainvoltage impulses for controlling the cathode-ray tube system of theinvention in accordance With one embodiment thereof.

Referring to Figure 1 the cathode-ray tube system shown thereincomprises a cathode-ray tube I0 containing, within an evacuated envelopel2, a conventional beam generating and accelerating electrode systemcomprising a cathode I4, a control electrode I6 for varying theintensity of the beam, a rst anode or focusing electrode i8, and a beamaccelerating electrode 20 which may consist of a conductive coating onthe inner Wall of the envelope and which terminates at a point spacedfrom the end face 22 of the tube in conformance with well-establishedpractice. Suitable heating means (not shown) are provided formaintaining the cathode lll at its operating temperature. The electrodesystem so dened is energized by a suitable source of potential shown asa battery 24 having its negative pole connected to ground and itspositive pole connected to the anode i8 and by a battery 2t having itsnegative pole connected to the positive pole of the battery 24 and itspositive pole connected to the accelerating electrode 20. In practicethe battery 24 has a potential of l to 3 kilovolts whereas the battery2S has a potential of the order of 10 to 20 kilovolts.

A deflection yoke 21 coupled to horizontal and vertical deflectioncircuits of conventional design is provided for deecting the generatedelectron beam across the face plate 22 of the cathode-ray tube to form araster thereon.

The end face plate 22 of the tube is provided With a beam interceptingstructure 28 shown in detail in Figure 2. In the arrangement shown inFigure 2 the structure 28 is formed directly on the face plate 22,however, it should be well understood that the structure 28 may beformed on a suitable light transparent base which is independent of theface plate 22 and may be spaced therefrom. In the arrangement shown, theend face 22 which in practice consists of glass having preferablysubstantially uniform transmission characteristics for the variouscolors in the visible spectrum, is provided with a plurality of spacedgroups of elongated parallel arranged stripes 3d, 32 and 3G, of phosphormaterial which, upon impingement of the cathode beam, fluoresce toproduce light of three different primary colors. For example, the stripe30 may consist of a phosphor which upon excitation produces red light,the stripe 32 may consist of a phosphor which produces green light andthe stripe 34 may consist of a phosphor which produces blue light. Eachof the groups of stripes may be termed a color triplet and, as will benoted, the sequence of the stripes is repeated in consecutive order overthe area of the structure 28. Suitable materials constituting thephosphor stripes 3S, 32 and 36 are Well known to those skilled in theart as well as the method of applying the same to the face plate 22, andfurther details concerning the same are believed to be unnecessary.

In the arrangement shown, the indexing signal is produced by utilizingindexing stripes of a given secondary-emissive ratio differing from thesecondary-emissive ratio of the remainder of the beam interceptingstructure and for this purpose that of the material '.oficoating 3S.

'the .structure 28 'further comprises a :thin electhe phosphor .stripes30,53-2Jand1'35l and .preferably further constitutes a mirror forreflecting .light generated .at thephosphorf stripes. in practice the.layer ..36 is .la .light .reflecting 1 aluminum coating which is formed.inwell knownmanner.

lar to aluminum, and y having `a ksecondary-emissive ratio detectably.distinct :from 4that `.of .the material ,of the `,indexing imember,.may .also be used. Such other metals .may be, Lfor example, magnesium:or beryllium.

Arranged on-the coating .36.:and: spacedbetween adjacent groups of.color stripes are :indexing stripes 3.8 consisting of a materialLhaving la :secondary-.emissive ratio detectably diierent .from Thestripes 38, usually ,of gold, may consist `of sother high atomic numbermetalssnch.as platinumior tungsten or of amixture,containingicesiumoxide as previously pointed out.

The beam interceptingtstructure sorconstituted is connected to the,positivepoleof'the.batteryt by meansof a suitablelead attachedtothealuminum coating 3S.

interposed between the end :of the .accelerating anode 2c and the beaminterceptingstructure 28 is an output collector electrode im consistingof a ring shapedcoating forexample, .of

.graphite or of silver, on the wallof .theenvelope Electrode d@ .iisenergized .through a load resistor 42 by a suitable source dlhshown asabattery. rThe source die may have a .potential of 4the order of 3kilovolts.

The cathode-ray beamin its vertical andhorizontal travel across thesbeamintercepting structure 23 (see Figure 2) impinges successively ,on thecoating 36 and the indexing'stripes producing through the load resistori2 .a secondaryemissive current having components which tend to mask orcontaminate the .index signal voltage to a greater or lesser extent. :Inorder .to provide an indexingsignal which is clearly distinguished fromany contaminating influences and in accordance with the invention, theintensity of the electron beamis momentarily made to assume apredetermined value during the intervals in which the Vbeam `impinges onthe inponents `so that an output voltage is produced across the loadimpedance i d2 Aconsisting predominantly of an indexing componentandhaving spurious or masking components present only to a minor extent.

The indexing signals so produced'areused for controlling the instancesatwhich the video color signals are applied to the cathode-ray tubeduringthe movement of the beam across .the .beam intercepting rstructure:28;andfurther .provide the .control by .which the intensity ofthe`cathodevcapablecof. formingaicoatingintheimanner.simi- T10 6raybeamfis'automaticallymodied :to thedesired value duringitsimpingementxon `the indexing stripes. More specifically, :the indexingavoltage appearing across zthe :load resistor t2 applied by'means of aresistance-:capacitance networkwi and il to the input of .an '.amplierF-8 containing an amplitude limiter `of Iconventional -zdesign .by meansof which; any .spuriousmodulation appearing on'the indexing Vsignalszisremoved. .Amplier d8. is characterized bysufcientgainLto amplify the.indexing signals .supplied 'thereto :to a `conveniently lusable level,'and -may .be adapted to do so Withoutidistortion'of the indexingpulseWave-form, althoughithis isznot .essential vso long as Athephasecharacteristics of .the amplifier Aare such that :the positivepeaks of the .-amplied output signals therefrom occui` in :predeterminedtime relationship to .the times `of :occurrence of peaksv produced inthe signal at theload'. resistor 42 in response to .impingement .of thecathoderay beam on the indexing stripes.

The output signals .from amplifier aaaresupplied to the input of `a.delaylline Eil, .which 'is provided with three taps '5d and 56. Deia?line 5s may comprise aseries of niter sections designed in accordancewith :principles weil known in theart so as `to .provide .atotal delay.for signals passing therethrough which .is at least as .great as theaverage Vtime required for the cathode-ray beam to :scan .from thecenter of one indexing stripe 33 to the :center of v.thenext.subsequently-impinged indexing stripe andis preferably terminatedin its-characteristic impedance so as to minimize reflections from thetermination thereof.

Tap 52 isspacedfromvthe input of delay line .Et by an .amount sufficientto 'provide a signal delay therebetween substantialy `equal to theaverage time .required 'for f the cathode-ray` beam .to sweep vfrom thecenter of an indexing stripe to the center of the adjacent red phosphorstripe 3&5, tap 54 is spacedfrom tap52 'by an amount suiiicienttoprovide a value of signal delay therebetween substantially equal `:totheaverage time required for the cathode-ray beam to travel from the'centeroffa red .phosphorstripe to the center of the next adjacent greenphosphor stripe 32, While tap 56 is spaced from tap 5d by anl amountsucient to provide a signal delaysubstantially equal to the average timerequired for the cathode-ray beam to sweep from the vcenter of a greenphosphor stripe to the center ofthe next adjacent blue phosphor-stripe35. In practice, and assuming a uniform placing-of the color andindexing stripes 3Q, 32, l3ft-and 38, the taps at the delay .lineprovide signals having displacements of l", 180 vand270 relative to thephase position of the index signalapplied `to .the input of the delayline.

`For the reproduction of a color .image on the face plate ofthecathode-ray tube, .there are provided color signal input terminals6i?, S and 'fili Which are supplied from Aa television receiver withseparate signalsindicative of themed, green and blue components oftheltelevised scenefrespectively, which signals preferably have had theirD.-C. components restored, and are of such polarity that the Amorepositive portionsthereof correspond Ato `.darker regions of thetelevision image. .The system then operatesto sample these three colorsignals in sequence so .that .the red video signal controls thecathode-ray beam in- .tensity upon impingement of the red vstripe B ,ofVthebearn interceptingstructure 28,'the green vdeo .signalviscontrolling .upon :impingement of the green stripe 32 and the blueVideo signal controls the beam intensity when the blue stripe 313 isimpinged. Accordingly, the three video input signals are supplied tointensity-controlling electrode l5 through sampling tubes SS, 68 and Trespectively. Sampling tube t6 may comprise a pentagrid vacuum tubewhich has its suppressor and cathode grounded, its second and fourthgrids connected to a suitable source of positive screen potential, itsthird grid supplied with the red video signal to be sampled, its firstgrid supplied with a sampling signal for rendering tube (it conductiveonly during predetermined portions of the sampling signal, and its plateconnected to a source of positive potential designated B| through aplate load resistor i2 and to the control grid I6.

`Sampling tubes 63 and l0 may be substantially identical with samplingtube 66, being supplied at their respective third grids with the greenand blue vdeo signals, respectively, and having their respective platesconnected to the source of potential B+ through the common plate loadresistor l2. By supplying each of the colorsignal sampling tubes, at thefirst grids thereof, with sampling signals whose positive peak valuescoincide in time with impingement of the corresponding color stripesarranged on the beam intercepting structure l5, the color samples areapplied to intensity-controlling electrode I6 at the proper times.

The signal at tap 52 constitutes a red-signal sampling signal which issupplied through a resistance-capacitance circuit 'M to the first gridof red signal sampler tube 66 so as to actuate the same and therebyapply a sample of the red video input signal to theintensity-controlling electrode I6 of cathode-ray tube l0. The timeconstant oi resistance-capacitance network l@ is suiiiciently long,compared to the period of the sampling signal from tap 52, so thatleveling upon the peaks of the sampling signals supplied thereto fromtap 52 is eiected, and actuation of sampling tube 65 is caused to occuronly during predetermined relatively brief intervals surrounding thetimes at which the sampling signal attains its peak values. Similarly,the signal at delay line tap d is Supplied through resistancecapacitancenetwork 'I6 to the first grid of sampler tube 68 so as to effectsampling of the green video signal when the sampling signal at tap 5dattains its maximum values. Finally, the signal at tap 5S is suppliedthrough resistancecapacitance network 18 to the iirst control grid ofblue sampler tube l0, so as to effect actuation thereofcontemporaneously with the attainment of peak values by the samplingsignal at tap 56.

As above noted and by reason of the resistancecapacitance networks Td,'it and i8 each of the sampling tubes 66, 58 and 'I0 is heldnon-conductive except for the periods during which a sampling pulse isapplied thereto from the delay line 50. Since the sampling pulses appearat 90, 180 and 270 intervals only, there will be periods correspondingto the 0 phase intervals when none of the sampling tubes are conductive.During these non-conductive periods of the sampling tubes a minimumvoltage drop occurs across the load impedance 'l2 so that the grid EEcorrespondingly achieves its maximum positive potential. The amount bywhich the potential of the control electrode I6 exceeds the potential ofcathode lli, and thus the intensity of the cathode-ray beam during thenon-conduction intervals of the sampling tubes, may be adjusted byvarying the potential of the cathode I4, for example, by connecting thecathode through a resistor to the movable tapping of a potentiometer 82connected to a suitable source of positive potential as shown.

The periods of 0 phase intervals, when none of the sampling tubes areconductive, occur in synchronism with the periods of the indexingsignals applied to the delay line 50 and therefore occur in synchronismwith the intervals during which the cathode-ray beam impinges on theindexing stripes 38. Asa result of the foregoing, the cathode-ray beamwill assume a maximum intensity value during those intervals when thecathoderay beam impinges on the indexing stripes and an indexing signalof correspondingly high amplitude value Will be produced.

It is apparent from the foregoing, that if the indexing stripes areconstituted by a fluorescent material which emits light in the invisibleportion of the spectrum, i. e. of zinc oxide emitting in theultra-violet region, and a photo-sensitive collector detector isutilized instead of the secondary emissive collector 40, the same modusoperandi obtains and indexing signals having indexing components whichare magnified relative to any spurious components are produced.

In practice the length of the pulses constituting the sampling signalsis less than one-fourth of the period between successive pulses of theindexing signal such as shown in Figure 1 by the Wave forms as A, B, Cand D for the red, green and blue sampling tubes and the indexing signalrespectively. This may bring about a condition wherein all of thesampling tubes are rendered non-conductive for short periods between theintervals at which the successive red, green and blue video signals aresampled corresponding to the intervals I, 2, 3 and ll shown in Figure 1.By reason of this action, the cathode-ray beam increases to its maximumintensity value during these nonconducting intervals and maycorrespondingly excite the leading and/or lagging edge of the colorstripes to an intensity not indicated by the video information.

lin accordance with one embodiment of the invention this difculty isovercome by suitably extending the length of the sampling pulses so thateach pulse has a length at least equal to onei'ourth of the periodbetween the pulses of the indexing signal as shown in Figure 3 by theWave forms A', B', C and D respectively whereby at least one samplingtube is conductive during the scanning of the color triplets by thecathode-ray earn. This may be accomplished by appropriately adjustingthe constants of the resistancecapacitance network 55 and 41 and oftheampliiler-limiter 48 so that indexing pulses having a length ofone-quarter of the interval between pulses are produced at the output ofthe amplifierlimiter 118. The amplier-limiter d8 may include suitablefeed back networks to ensure against a progressive increase in thelength of the output pulses from the amplifier-limiter 48.

Alternately, the stripes 30, 32 and 34 as well as the stripes 38 may bespaced apart by a distance corresponding to the intervals I, 2, 3 and 4as shown in Figure 2 whereby, at the instants that the beam reaches theabove indicated maximum intensity value, it is positioned between thestripes and no undesirable visible light is produced by the cathode-raytube.

In a further arrangement, the above noted difficulty is avoided byextinguishing the cathode-ray beam during periods corresponding to theperiods agesaaee I; 2, Slandi More particularly; and inthe-arrangementshoW-n in Figure'w 1 f there isl coupled to the outlet of`amplifiereliiniterJ 4&2 and to thee-tapping'points 521; 5dand'iiofithedelaylinef-50 suitable isolation phaseeinverter-'stages' 84;36'; 88 and S'frespectively, having their outputs4`v connected inparallel wherebyan-output voltage is'- produced constituted' bypulses-extending ina-` positive di rection during the intervals I; 2; 3iand 45 asshown byth'ewave form indicated by tliereferenceE. The voltageso producedis applied' throughav suitable amplier'dil to the-cathodeHlof' the tube Illandtsince there is thusiapplied afhighpositivepotentiall tothe cathode, during the.. intervalsin question thecathode-ray beam is extinguished during such intervals.

While-,I have,describedmyfinvention by means of.,specic examples andinspecicembodiments I do not wish to be limited theretorfor obviousmodifications will occur` to those skilled Iinthe art without departing.from thespiritfandscopeof the invention.

What I claim is:

l. A cathode-ray'A tubesystemcomprising a cathode-ray tube having asourcerof anfelec'tron beam, means to vary thefintensity'of saidbeamandfabeam intercepting structure;A said beanninterceptingstruoturehaving iirstportions .thereof spaced apartl andcomprisingiaipluralityof/ ele-- ments adaptedto produce light' uponimpinge- `ment by saidbeam, saidbeamintercepting'strucL ture havingsecond portions arranged' between said firstportionsspaciallyfdisplaced'from all of the said light producingelements, said second portions being adapted toproduce an outputsignalwhensaid beam impingesthereon; means to periodically deect saidbeamacross-saidibeam intercepting structure to thereby impinge said beamon said first andi secondi portions, input means adaptedA to providezasignal quantity having` amplitude variations within given values in.dicative of desired variations of' the intensity. of

thev light produced by,V said'light` producing. ele- A values whensaidbearn.impingessaiddightpro-l ducing.- elements, andmeans-responsivetosaid output-signal to vary the intensityfof saidbeam to .a secondgiven`value independentlyof .thefamplitude of saidsignal quantity when.` saidbeam impinges Yon said second portions;

ZFA. cathode-ray tube systemas claimed in claim` l wherein said meansresponsive to-said output voltage increases. the intensity of said beamto a. value greater than said given intensity values independently ofthe amplitude: of said signal quantity when said beam impinges saidsecond' portions:

3. A cathode-ray-tubefsystem-forrproducing a color television image,comprising a cathode-ray. tube having a source of an electronbeam,.means to vary the intensity'of'saidbeam anda. beam interceptingstructure', said beam intercepting structure having first' portionsthereof spaced apart, eachofsaid rst' portions-comprising a pluralityof' consecutively arranged stripes of fluorescent material each adaptedto produce light of a diierent color upon impingement by said beam, saidbeam intercepting structure having second portions arranged between saidfirst portions spacially displaced from all of said lightprodiioingistrip'es, saidf'secondfportions being adapted to'fprodiiceanoutput -signalwhen l said f beam f impingesithereon, means toperiodically deflect said beam'4 acrosssaid beamy interceptingstructureV to therebyY impinge saidbeam on saidfrst and second portions,input means-for aplurality of video Waves each'1liaving-amplitudevariations indicative of a given color component of saidimage, meansforapplying saidvideo waves in the'vform of consecutive pulses to saidcontrol electrode when said beam' impingesl said" light producingstripes to thereby vary the intensity of said beam within givenintensityvalues` when said beam impinges said light producing stripes, andmeans-responsive to saifdoutputsignal'to increase the intensity ofsaidilceanrto`l predetermined value greater than said given intensityValues independently of the amplitudes of saidvideo waves-when said beamimpingessaidsecond portions.

4; Ai-'cathode-ray tube system as claimed in claim Bwherein-thesaidconsecutive stripes of iiuorescent material are spaced apart a givendistance-and'theconsecutive pulses ofthe video signal applied to thecontrol electrode are spaced apart byVv a timeinterval corresponding tosaid given distance.

5l A-- cathode-ray tubeA system as claimed in claim 3 wherein the saidconsecutive pulses of the-video signal applied-to the control electrodeconstitute spaced groups of contiguous pulses.

6. A cathode-ray tube system as claimed in claim 3`` wherein the saidmeans responsive to Said output signal comprises a sampling systemcoupled* to said'control electrode and to said inputmeans, means coupledto said second portions of said beam intercepting structure toproducefspacedgroupsof sampling pulses to actuate said samplingfsysteminvsynchronism with the impingement of'saidfbeam on said light producingelements, andmeans coupled to saidf sampling system and to said controlelectrode to increase the intensity of said beam to said givenpredetermined value during the intervals between said spaced'groups of`sampling pulses.

'72 A cathode-rayl tube system for producing a color television image,comprising a cathoderayt'ube `having a cathode source of an electronbeam, al control electrode for varying the intensity of the beam, a beamintercepting structure having first portions thereof spaced apart, eachoffsaid portions comprising a plurality of stripes of fluorescentmaterial each producing light of adierent color when said electron beamimpinges thereon, and said beam intercepting structurehaving-intermediate said first portions and spacially displacedL fromall of said light producing stripes second portions comprising amaterial having ar given response characteristic when' said electronbeam'impinges thereon and means to produce an` output signal indicativeofthe response characteristic of said second portions, means toperiodically deect said beam across saidrbeam intercepting structure tothereby impinge said beamisuccessively on said first and-second'portions, a video .signalr sampling system comprising a plurality. of'normally closed transmission paths having individual. input circuits andav common output circuit, means to apply to" each` ofl said input`-circuits individual videoI voltages each indicative' of a` given colorcomponent of said image, means to couple said control electrode to saidcommon output circuit at a portion thereof producing in said tube anelectron beam of given intensity when said paths are simultaneouslyclosed, means to derive from said output signal a plurality of samplingpulses consecutively arranged in spaced groups and having a timeinterval distribution corresponding to the space interval distributionof said light producing stripes, and means to apply said sampling pulsesto said transmission paths to open said paths in consecutive order forgiven time intervals and thereby apply to said control electrode saidindividual video voltages in sequence and in synchronism Ywith theimpingement of` said beam on said stripes of iiuorescent material and tomaintain said paths simultaneously closed for a second given timeinterval in synchronism with the impingement of said beam on said secondportions to thereby vary the intensity of said beam to said given valueindependently of the amplitude of said video voltages when said beamimpinges said second portions.

8. A cathode-ray tube system as claimed in claim 7 wherein said stripesof uorescent material are spaced apart by given distances, and thesampling pulses of each of said spaced groups are spaced apart by timeintervals corresponding to said given distances.

9. A cathode-ray tube system as claimed in claim '7 wherein the samplingpulses of each of said spaced groups occur during contiguous timeintervals.

10. A cathode-ray tube system as claimed in claim 7 wherein the samplingpulses of each of said spaced groups are spaced apart by a given timeinterval and further comprising means responsive to said output signalcoupled to said cathode-ray tube to extinguish said beam during the saidtime interval between sampling pulses of each of said spaced groups.

11. A cathode-ray tube system for producing a color television image,comprising a cathoderay tube having a cathode source of an electronbeam, a control electrode for varying the intensity of the beam, a beamintercepting structure having rst portions thereof spaced apart, each ofsaid portions comprising a plurality of stripes of uorescent materialeach producing light of a different color when said electron beamimpinges thereon, and said beam intercepting structure havingintermediate said rst portions and spacially displaced from all of saidlight producing stripes second portions comprising a material having agiven response characteristic when said electron beam impinges thereonand means to produce an output signal indicative of the responsecharacteristic of said second portions, means to periodically deect saidbeam across said beam intercepting structure to thereby impinge saidbeam successively on said rst and second portions, a Video signalsampling system comprising a plurality of discharge tubes having inputand output circuits, means coupled to said input circuits to maintainsaid discharge tubes normally non-conductive, means to apply to each ofsaid input circuits individual video voltages each indicative of a givencolor component of said image, an impedance element connected in commonwith said output circuits, means to couple said impedance element tosaid control electrode and to a source of positive potential to therebyproduce in said cathode-ray tube an electron beam of given intensitywhen said discharged tubes are rendered simultaneouslyy non-conductive,means to derive from said output signal a plurality of sampling pulsesconsecutively arranged in spaced groups, and means to apply said pulsesto said input circuits to thereby render said discharge tubes conductivein consecutive order for a given time interval in synchronism with theimpingement of said beam on said stripes of fluorescent material and tomaintain said discharge tubes simultaneously non-conductive for a secondgiven time interval in synchronism with the impingement of said beam onsaid second portions to thereby vary the intensity of said beam to saidgiven value independently of the amplitude of said video voltages whensaid beam impinges said second portions.

12. A cathode-ray tube system as claimed in claim 11 wherein thesampling pulses of each of said spaced groups are spaced apart by agiven time interval and further comprising a transmission path having aninput circuit and an output circuit, means to apply said sampling pulsesto said input circuit, and means coupled to said output circuit tocombine said sampling pulses and apply the same to the cathode of saidcathode-ray tube in a sense extinguishing the said beam during the saidtime interval between sampling pulses of each of said spaced groups.

13. A cathode-ray tube system comprising a cathode-ray tube having anelectron responsive member, means for generating electrons and fordirecting the same in beam formation towards said member and means forvarying the flow of said electrons from said generating means, saidelectron responsive member having first portions thereof spaced apartand comprising a plurality of elements adapted-to produce light uponelectron impingement, said beam intercepting member having secondportions arranged between said first portions spacially displaced fromall of the said light producing elements, said second portions beingadapted to produce an output signal upon electron impingement, means forscanning said electrons in beam formation across said beam interceptingmember, means for providing a signal quantity having amplitudevariations within given values indicative of desired variations of theintensity of the light produced by said light producing elements, meansfor applying said signal wave to said electron now varying means therebyto vary the intensity of electron now from said generating means withingiven intensity values during the scanning of said light producingelements, and means coupled to said electron flow varying means andresponsive to said output signal for varying the intensity of electronflow from said generating means to a given value independently of theamplitude of said signal quantity during the scanning of said secondportions.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,343,825 Wilson Mar. 7, 1944 2,463,535 Hecht Mar. 8, 19492,490,812 Huffman Dec. 13, 1949 2,530,431 Huffman Nov. 21, 19502,545,325 Weimer Mar, 13, 1951

